1. Field of the Invention
The present invention relates to a device for a vehicle sheet.
2. Background Art
In a cabin structure of a vehicle, such as an automobile or the like, it is generally known as disclosed in Japanese Patent Application Laid Open Publication No. 2001-239870A to divide the cabin into a passenger compartment and a luggage compartment at the back of the cabin by a sheet back of the rearmost seat of a plurality of seats arranged back and forth and to fold the seat back forward so as to be laid over a seat cushion for using the upwardly facing back of the seat back as a luggage table, namely, so as to expand the luggage space toward a passenger compartment.
Referring to generally known vehicle seats, Japanese Patent Application Laid Open Publication No. 2005-41406A proposes that laying of a seat back over the seat cushion and returning thereof to a raised state are performed by an electric motor. In this proposal, a limit switch detects completion of the laying of the seat back thereover or completion of development (raising) and, then, stops the electric motor. It is further known as disclosed in Japanese Patent Application Laid Open Publication No. 2004-249962A that the sheet is stored in a storage wholly section behind the seat with the seat back laid over the seat cushion, that the storage and returning to the original state thereof are performed by the electric motor, and that a manipulation switch which returns to an OFF state upon release of manipulation therefore is arranged at the rear of the seat (in a luggage compartment).
The electric motor employed for raising the seat back from the forwardly folded state as above mitigates burden on the user. In employing the electric motor, it can be contemplated to arrange a momentary type manipulation switch at the luggage compartment or the like at the rear of the seat so as to operate the electric motor only when the manipulation switch is pushed.
Employment of such a momentary type manipulation switch, however, delegates the user to determine the posture of the seat back. Accordingly, even if the user determines the raised angle of the seat back at a degree that the user thinks it comfortable and stops the electric motor to set the seat back at the determined angle, expected comfortableness would not be obtained in some cases. For example, the seat back is raised excessively to cause the user to feel uncomfortable or is reclined so backward to cause the user to feel uncomfortable and to narrow the luggage space behind the seat back.
For tackling this problem, a mark that indicates a position of the seat back which brings the seat back to a predetermined position may be provided. In this case, the user can turn off the manipulation switch while confirming the raised position of the seat back by watching the mark. Even in such a case, however, the user may release his/her hand too early or too late, which invites impossibility to stop the seat back at the desired raised position without failure.
Alternatively, a stopper may be provided for stopping the seat back at a predetermined raised position. Specifically, the seat back is raised by the operation of the electric motor, and overcurrent flows in the electric motor upon abutment of the seat back on the stopper. When the overcurrent is detected, electric conduction to the electric motor is cut. In this case, however, large force is applied to the seat back, the stopper, and the like until the electric motor is stopped from the time when the seat back abuts on the stopper, and therefore, the device for the seat vehicle is liable to be broken. For tackling this problem, a part of the stopper or the seat back may be reinforced. This reinforcement, however, involves an increase in weight of the vehicle.
Another device may be considered. Namely, the electric motor is used not only for raising the seat back from the forwardly folded state but also for folding the seat back forward from the raised state. In this device, the seat back would be folded forward by careless operation of the electric motor though an object would be placed on the seat. Further, it is necessary for folding the seat back forward to manipulate an activation switch for the electric motor. Further, it takes considerable time from the time when the activation switch is turned on to the time when the electric motor is activated, the seat back is folded forward, and then, the electric motor is stopped. Therefore, quick forwardly folding of the seat back cannot be attained. Further, employment of the electric motor for forwardly folding the seat back increases power consumption in the automobile.
To tackle this problem, a scheme can be considered in which the seat back is raised by the electric motor and is folded forward by biasing means, such as a spring or the like, so that seat back becomes in the forwardly folded state immediately upon manual lock release of the seat back.
However, the electric motor for raising the seat back restrains forwardly folding of the seat back because the electric motor engages with the seat back or the vehicle (or the seat cushion) through transmitting means, such as a gear. In detail, in order to fold the seat back forward, the output shaft of the electric motor must be rotated in a direction reverse to that for raising the seat back, and therefore, the electric motor restrains forwardly folding thereof. For this reason, only by the biasing means, the seat back may stop being folded forward in the middle, so that the seat back may not be in the predetermined forwardly folded state unless the user pushes the seat back from above. Further, the base end of the seat back may be rubbed with the rear end of the seat cushion in forwardly folding of the seat back, to cause friction resistance in forwardly folding of the seat back. In this case, not only restraint of the electric motor but also the friction resistance applied cause difficulty in setting the seat back to the predetermined forwardly folded state only by the biasing means, such as a spring or the like.